Why is glass transparent yet copper metal is opaque?

  • 3 Replies

0 Members and 1 Guest are viewing this topic.


Offline labview1958

  • Sr. Member
  • ****
  • 104
    • View Profile
Why is glass transparent and metallic copper is opaque?

[MOD EDIT - Please try to phrase your post titles as questions, in line with forum policy (it also helps people to find what they are looking for and translates into many more responses for your posts. Thank you.]
« Last Edit: 19/03/2009 09:56:01 by chris »


Offline Soul Surfer

  • Neilep Level Member
  • ******
  • 3345
  • keep banging the rocks together
    • View Profile
    • ian kimber's web workspace
Why is glass transparent yet copper metal is opaque?
« Reply #1 on: 19/03/2009 10:17:02 »
The most important feature about copper that makes it opaque is that it is a conductor of electricity.  This is because the atoms in the solid are bonded together in such a way to allow the outer electrons freedom of movement through the material.  Because it is a conductor it effectively "shorts out" the electrostatic part of electromagnetic waves (light)and this reflects the energy from the surface and prevents it from flowing through the body of the copper in a coherent way. 

Now glass is an insulator and electromagnetic energy can enter the material but that's not enough to make it transparent The next requirement is that the material itself does not absorb the frequencies of light that are being used.  Many insulators are coloured because they absorb light of different frequencies.

Finally there is one important additional requirement.  Glass is a uniform material and is often prepared with a smooth surface this ensures that the light is not dispersed through the material and glass is transparent.  Only a very slight disturbance of the surface will make the glass frosted or obscured.
« Last Edit: 19/03/2009 20:01:58 by Soul Surfer »
Learn, create, test and tell
evolution rules in all things
God says so!



  • Guest
Why is glass transparent yet copper metal is opaque?
« Reply #2 on: 19/03/2009 10:28:32 »
Brill explanation!
Well put.


Offline yor_on

  • Naked Science Forum GOD!
  • *******
  • 12339
  • (Ah, yes:) *a table is always good to hide under*
    • View Profile
Why is glass transparent yet copper metal is opaque?
« Reply #3 on: 19/03/2009 19:47:55 »
Interesting, when I think of why you can see through glass I think about its molecular structure primarily. Its ordered similar to a fluid but rigid, I guess that's why some say it is a very slow running 'fluid' :). If you consider water, or a gas the light have ways through it, the molecules don't absorb as much of the viewable spectrum as there are 'holes' between them. Also our viewable light doesn't get absorbed as much by the electronsclouds in glass. But that depends on what type of glass it is.
« Last Edit: 19/03/2009 19:50:53 by yor_on »
"BOMB DISPOSAL EXPERT. If you see me running, try to keep up."